Awtar Singh

Systemic Information for Future Perspectives in Litchi Crop Improvement

Litchi (Litchi chinensis Sonn.) is a subtropical evergreen fruit crop of the Sapindaceae family. Over the years, significant growth in production and productivity coupled with the fast-expanding market of litchi has been recorded at both the national and international level. Most commercial cultivars in litchi have been clonally selected under Chinese or Indian conditions and have been adapted to a limited climatic condition. Disease infestation in litchi has been a long-term debate in the horticulture and agriculture sector. Keeping the damage factor as a prime concern, clonal selection as the basis of cultivar selection must rely on limited characteristics such as systemic susceptibility in terms of fruit size, quality, and period of maturity, which narrows down the diversity, focusing on only a few commercial traits. Hence, creation of variability within the litchi gene pool is of paramount importance to yield desirable characters such as precocity, dwarfness, regularity of bearing, wider adaptability, and resistance and avoidance of pests and disorders. The heterozygosity of litchi produces a wide extent of variability, which serves as the baseline for new selections through harnessing precocious genes and exploiting natural hybrid vigour and other genetic manipulations. Different strategic efforts on a breeding programme need to be undertaken on a large scale with considerations of a comprehensive survey of various genotypes and trait inheritance patterns, raising a large population of open pollinated seeds with known parentage, mutation breeding because of obvious difficulties with traditional litchi breeding and the lack of pure lines. This context provides the basic information for further improvement and genetic enhancement of the breeding programme in litchi disease resistance.

Transition Metal Nitrides: A First Principles Study

Abstract The present work describes the structural stability and electronic and mechanical properties of transition metal nitrides (TmNs: B1 cubic structure (cF8, Fm 3‾

Genetic diversity in seedling populations of Mango

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Narrow genetic base of Indian litchi (Litchi chinensis) cultivars based on molecular markers

m)) using first principles density functional theory (DFT) within generalized gradient approximation (GGA). The lattice constant of TmNs increases with increasing the atomic radii of the transition metals. Stability of the TmNs decreases from IVB to VIB groups due to increase in formation energy/atom. The bonding characteristics of these nitrides have been explained based on electronic density of states and charge density. All the TmNs satisfy Born stability criteria in terms of elastic constants except CrN and MoN that do not exist in equilibrium binary phase diagrams. The groups IVB and V–VIB nitrides are associated with brittle and ductile behaviour based on G/B ratios, respectively. The estimated melting temperatures of these nitrides exhibit reasonably good agreement with calculated with B than those of the C11 for all nitrides.

Genetic diversity analysis of indigenous and exotic apple genotypes using inter simple sequence repeat markers

The pummelo (Citrus grandis Merr.), the largest fruit size in citrus species, is an underutilized fruit in India. Pummelo in Bihar is mostly grown as homesteads and this fruit is to be developed as potential table fruit because of thick rind, easy to handle and transport. Genetic diversity is an important factor in any crop improvement programme for obtaining high yielding cultivars. Variation among seedling progenies is a rule in pummelo since it is monoembryonic Citrus spp. This study was conducted through four cell analysis in the five project communities under the UNEP-GEF project at the Pusa Site, Bihar during 2012 with aim for estimation of genetic diversity for physico-chemical traits, selection of superior clones and to draw the interrelationships between observations for precise characterization of pummelo seedling. Superior plants were also identified based on the highest yield i.e. number of fruits/ plant (> 300). Statistical analysis for physico-chemical parameters revealed significant differences among the selected plants for the 12 horticultural traits indicating the higher variability. Principal Component Analysis (PCA) and cluster dendrogram performed on the basis of studied parameters showed continuous variation in the fruit physico-chemical traits and many groups were formed, indicating existence of large and continuous variation. The first four PCs contributed 68.30% of the variability for fruit quality and PC1 accounted for 30.44% (acidity percentage) followed by fruit length (PC2), fruit width (PC3) etc. The maximum coefficient of variation was found in in case of rind thickness, 100 seed weight and acidity percentage. A large number of variability of pummelo with seedling origin and monoembryonic helps in identification of 4 pummelo clones for pulp colour (2 each for dark red flesh and pink flesh) with excellent eating quality, 9 superior clones were identified for profuse bearing with red fleshed and early. The above variation in the selected pummelo seedlings can be exploited for development of superior varieties, marketing and maintenance of exiting superior clone and above all grower can be ensured livelihood security through homestead farming practices in the community.

Combining ability studies of yield and its contributing traits in tomato (Lycopersicom esculentum mill.)

The genetic improvement of mango (Mangifera indica L.), a native of India, has been largely through selection among seedling populations or propagating elite clones and such efforts have resulted in the identification and cultivation of improved commercial varieties. Development of better cultivars by traditional method using morphological traits, although highly heritable, is slow because of long juvenility and being expensive. Farmers of Pusa, Bihar have been conserving high levels of intraspecific diversity of mango in old orchards mostly located along the Gandak River. These orchards are often poorly maintained as revenues obtained are small compared to income from other farm activities; however these old orchards harbour a highly diverse population of traditional mango varieties and seedlings, with trees over 80 years old. Hence a survey was conducted in five communities for documenting the mango diversity found in native landraces. Sixteen superior mango varieties of endemic value and importance were evaluated for table, sucking and pickling purposes on the basis of physical appearance and chemical attributes. Out of these, six were found suitable for table, five for sucking, three for pickle and two for dual purpose (sucking and table). Studies revealed a clone from Bhuskaul community with fruit weight up to 420.0 g with TSS 27.400B and having very thin stone and maturing by the end of August. The present study highlights the need for and demands of diversity rich areas of Pusa community in Bihar to conserve and protect seedling mangoes for the benefit of posterity with high value traits for future promotion. Furthermore, the characterization work was captured in fruit catalogues and shared back with the farming community, which might have increased the awareness, interest and appreciation of the available mango diversity and the interest in the continuation of these old highly diverse mango orchards for home use and to explore the commercial potential of these orchards and various types.